"use strict";

/**
 * An $second pipeline expression.
 * @see evaluateInternal
 * @class SecondExpression
 * @namespace mungedb-aggregate.pipeline.expressions
 * @module mungedb-aggregate
 * @constructor
 **/
var SecondExpression = module.exports = function SecondExpression() {
	this.nargs = 1;
	base.call(this);
}, klass = SecondExpression,
	base = require("./NaryExpression"),
	proto = klass.prototype = Object.create(base.prototype, {
		constructor: {
			value: klass
		}
	});

// DEPENDENCIES
var Expression = require("./Expression");

// PROTOTYPE MEMBERS
proto.getOpName = function getOpName() {
	return "$second";
};

/**
 * Takes a date and returns the second between 0 and 59, but can be 60 to account for leap seconds.
 * @method evaluateInternal
 **/
proto.evaluateInternal = function evaluateInternal(vars) {
	var date = this.operands[0].evaluateInternal(vars);
	return date.getUTCSeconds(); //TODO: incorrect for last second of leap year, need to fix...
	// currently leap seconds are unsupported in v8
	// http://code.google.com/p/v8/issues/detail?id=1944
};

/** Register Expression */
Expression.registerExpression("$second", base.parse(SecondExpression));